The confrontation between Augustine and Pelagius did not end in a scholarly debate; it ended in a series of legal maneuvers. The most critical of these was the Synod of Diospolis in 415 CE, a proceeding that serves as a masterclass in the "dysfunction" of imperial justice.
Augustine and his allies—including the influential Jerome and the pupil Orosius—did not want a fair trial; they wanted a conviction. By pushing Pelagius toward Palestine, they moved him into a jurisdiction where he was an outsider. Orosius, acting as Augustine's proxy, attempted to use the "Carthage precedent" to claim that Pelagius's disciple, Caelestius, had already been condemned, thereby making Pelagius a "guilty by association" heretic.
The Synod of Diospolis reveals how the "Imperial Machine" often failed when it encountered actual diversity. The proceedings were characterized by a profound Linguistic and Cultural Divide:
While Pelagius escaped legal condemnation at Diospolis, the trial achieved Augustine's primary goal: Stigmatization. By forcing Pelagius into the courtroom, Augustine successfully shifted the public perception of Pelagius from a "respected monk" to a "defendant."
The trial functioned as a signal to the wealthy patrons of the era. It told them that associating with Pelagius was a legal risk. Ultimately, Pelagius was expelled from Jerusalem and allowed to settle in Egypt under Cyril of Alexandria, but his influence in the West had been surgically removed by the process of the trial itself.